The oceans of the world absorb a large part of the carbon dioxide released into the atmosphere by us burning fossil fuels, burning forests to make room for fields, etc. This have helped slow down global warming, but new studies shows that it might have a devastating effects on certain fish species such as clown fish. Tests performed on clown fish larvae have shown that increased levels of carbon dioxide can make them disoriented an unable to find a suitable home and avoid predators. The pH level in the ocean has dropped 0.1 since pre-industrial times due to the absorption of carbon dioxide and researchers believe that it will fall another 0.3-0.4 before the end of this century.

This increased acidicy of the water can cause serious problems for clown fish larvae, since clownfish larvae lose the ability to sense vital odours in more acidic waters – probably owing to the damage caused to their olfactory systems. Kjell Døving (Oslo University), co-author of the rapport that was published in US journal Proceedings of the National Academy of Sciences, says “They can’t distinguish between their own parents and other fish, and they become attracted to substances they previously avoided. It means the larvae will have less opportunity to find the right habitat, which could be devastating for their populations.“

The research indicates that other species might be affected in a similar way and might have a hard time finding their way to suitable habitats if carbon dioxide levels raises in the oceans.

About the study

The study was executed in such a way that the researchers checked how well clownfish larvae could detect smells in normal sea water (pH 8.15) and how well they could detect odours in more acidic water (at levels predicted to be a reality around the year 2100 and later). The test showed that at pH 7.8 the larvae stopped following scent trails released by reefs and anemones and started following sent trails they would normally avoid; scents that are associated with environments not suitable for clown fish. The larvae also lost the ability to use smell to distinguish between their parents and other fish. At pH 7.6 the larvae were unable to follow any kind of odour in the water, and instead swam in random directions.